Android example source code file (AbstractThreadedSyncAdapter.java)

This example Android source code file (AbstractThreadedSyncAdapter.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

abstractthreadedsyncadapter, account, accounts, android, atomicinteger, bundle, contentproviderclient, ibinder, isyncadapterimpl, log_sync_details, object, os, remoteexception, string, syncadapterthread, synccontext, syncresult, syncthread

The AbstractThreadedSyncAdapter.java Android example source code

/*
 * Copyright (C) 2009 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.content;

import android.accounts.Account;
import android.os.Bundle;
import android.os.IBinder;
import android.os.Process;
import android.os.RemoteException;

import java.util.concurrent.atomic.AtomicInteger;

/**
 * An abstract implementation of a SyncAdapter that spawns a thread to invoke a sync operation.
 * If a sync operation is already in progress when a startSync() request is received then an error
 * will be returned to the new request and the existing request will be allowed to continue.
 * When a startSync() is received and there is no sync operation in progress then a thread
 * will be started to run the operation and {@link #onPerformSync} will be invoked on that thread.
 * If a cancelSync() is received that matches an existing sync operation then the thread
 * that is running that sync operation will be interrupted, which will indicate to the thread
 * that the sync has been canceled.
 */
public abstract class AbstractThreadedSyncAdapter {
    /**
     * Kernel event log tag.  Also listed in data/etc/event-log-tags.
     * @Deprecated
     */
    public static final int LOG_SYNC_DETAILS = 2743;

    private final Context mContext;
    private final AtomicInteger mNumSyncStarts;
    private final ISyncAdapterImpl mISyncAdapterImpl;

    // all accesses to this member variable must be synchronized on mSyncThreadLock
    private SyncThread mSyncThread;
    private final Object mSyncThreadLock = new Object();

    private final boolean mAutoInitialize;

    /**
     * Creates an {@link AbstractThreadedSyncAdapter}.
     * @param context the {@link android.content.Context} that this is running within.
     * @param autoInitialize if true then sync requests that have
     * {@link ContentResolver#SYNC_EXTRAS_INITIALIZE} set will be internally handled by
     * {@link AbstractThreadedSyncAdapter} by calling
     * {@link ContentResolver#setIsSyncable(android.accounts.Account, String, int)} with 1 if it
     * is currently set to <0.
     */
    public AbstractThreadedSyncAdapter(Context context, boolean autoInitialize) {
        mContext = context;
        mISyncAdapterImpl = new ISyncAdapterImpl();
        mNumSyncStarts = new AtomicInteger(0);
        mSyncThread = null;
        mAutoInitialize = autoInitialize;
    }

    public Context getContext() {
        return mContext;
    }

    private class ISyncAdapterImpl extends ISyncAdapter.Stub {
        public void startSync(ISyncContext syncContext, String authority, Account account,
                Bundle extras) {
            final SyncContext syncContextClient = new SyncContext(syncContext);

            boolean alreadyInProgress;
            // synchronize to make sure that mSyncThread doesn't change between when we
            // check it and when we use it
            synchronized (mSyncThreadLock) {
                if (mSyncThread == null) {
                    if (mAutoInitialize
                            && extras != null
                            && extras.getBoolean(ContentResolver.SYNC_EXTRAS_INITIALIZE, false)) {
                        if (ContentResolver.getIsSyncable(account, authority) < 0) {
                            ContentResolver.setIsSyncable(account, authority, 1);
                        }
                        syncContextClient.onFinished(new SyncResult());
                        return;
                    }
                    mSyncThread = new SyncThread(
                            "SyncAdapterThread-" + mNumSyncStarts.incrementAndGet(),
                            syncContextClient, authority, account, extras);
                    mSyncThread.start();
                    alreadyInProgress = false;
                } else {
                    alreadyInProgress = true;
                }
            }

            // do this outside since we don't want to call back into the syncContext while
            // holding the synchronization lock
            if (alreadyInProgress) {
                syncContextClient.onFinished(SyncResult.ALREADY_IN_PROGRESS);
            }
        }

        public void cancelSync(ISyncContext syncContext) {
            // synchronize to make sure that mSyncThread doesn't change between when we
            // check it and when we use it
            final SyncThread syncThread;
            synchronized (mSyncThreadLock) {
                syncThread = mSyncThread;
            }
            if (syncThread != null
                    && syncThread.mSyncContext.getSyncContextBinder() == syncContext.asBinder()) {
                onSyncCanceled();
            }
        }

        public void initialize(Account account, String authority) throws RemoteException {
            Bundle extras = new Bundle();
            extras.putBoolean(ContentResolver.SYNC_EXTRAS_INITIALIZE, true);
            startSync(null, authority, account, extras);
        }
    }

    /**
     * The thread that invokes {@link AbstractThreadedSyncAdapter#onPerformSync}. It also acquires
     * the provider for this sync before calling onPerformSync and releases it afterwards. Cancel
     * this thread in order to cancel the sync.
     */
    private class SyncThread extends Thread {
        private final SyncContext mSyncContext;
        private final String mAuthority;
        private final Account mAccount;
        private final Bundle mExtras;

        private SyncThread(String name, SyncContext syncContext, String authority,
                Account account, Bundle extras) {
            super(name);
            mSyncContext = syncContext;
            mAuthority = authority;
            mAccount = account;
            mExtras = extras;
        }

        public void run() {
            Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND);

            if (isCanceled()) {
                return;
            }

            SyncResult syncResult = new SyncResult();
            ContentProviderClient provider = null;
            try {
                provider = mContext.getContentResolver().acquireContentProviderClient(mAuthority);
                if (provider != null) {
                    AbstractThreadedSyncAdapter.this.onPerformSync(mAccount, mExtras,
                            mAuthority, provider, syncResult);
                } else {
                    syncResult.databaseError = true;
                }
            } finally {
                if (provider != null) {
                    provider.release();
                }
                if (!isCanceled()) {
                    mSyncContext.onFinished(syncResult);
                }
                // synchronize so that the assignment will be seen by other threads
                // that also synchronize accesses to mSyncThread
                synchronized (mSyncThreadLock) {
                    mSyncThread = null;
                }
            }
        }

        private boolean isCanceled() {
            return Thread.currentThread().isInterrupted();
        }
    }

    /**
     * @return a reference to the IBinder of the SyncAdapter service.
     */
    public final IBinder getSyncAdapterBinder() {
        return mISyncAdapterImpl.asBinder();
    }

    /**
     * Perform a sync for this account. SyncAdapter-specific parameters may
     * be specified in extras, which is guaranteed to not be null. Invocations
     * of this method are guaranteed to be serialized.
     *
     * @param account the account that should be synced
     * @param extras SyncAdapter-specific parameters
     * @param authority the authority of this sync request
     * @param provider a ContentProviderClient that points to the ContentProvider for this
     *   authority
     * @param syncResult SyncAdapter-specific parameters
     */
    public abstract void onPerformSync(Account account, Bundle extras,
            String authority, ContentProviderClient provider, SyncResult syncResult);

    /**
     * Indicates that a sync operation has been canceled. This will be invoked on a separate
     * thread than the sync thread and so you must consider the multi-threaded implications
     * of the work that you do in this method.
     *
     */
    public void onSyncCanceled() {
        final SyncThread syncThread;
        synchronized (mSyncThreadLock) {
            syncThread = mSyncThread;
        }
        if (syncThread != null) {
            syncThread.interrupt();
        }
    }
}